A molecular dynamics simulation was conducted on hydrogen embrittlement at a crack tip of a single crystal of α-iron composed of {100} planes under uniaxial tensile load along the 100 direction on a nanometre scale at 293 K. The modified Morse pair-potential function of Fe-Fe and the Morse potential function of Fe-H were used to calculate the interatomic action force. A threedimensional model with 2618 iron atoms and from one to 260 hydrogen atoms segregated at the notched area was designed for the simulation. The general conclusion on hydrogen embrittlement of a single crystal of α-iron could be described qualitatively as the processes of cavity nucleation, cavity linkage and, finally, fracture. Cavity nucleation occurs on the (100) plane in the notched area of the specimen with more than three hydrogen atoms at the early stage of the deformation and does not depend on the hydrogen content. The cavities are linked to each other and fracture occurs on the plane with progressing deformation. The deformation step of cavity linkage and fracture decrease logarithmically with increasing hydrogen content, while neither the cavity nor the fracture occur, even at the maximum total deformation of 50%, due to blunting of the crack tip in the specimen without hydrogen.

No abstract

No abstract

Pd (en)2Cl2can be intercalated into graphite oxide layers with high efficiency. The Pd (en)22+intercalated graphite oxide was firstly synthesized by mixture reaction of Pd (en)2Cl2and graphite oxide, then it was reduced in solution with NaBH4and thereafter the graphene/Pd nanosized particle composites were obtained. The graphene composites were characterized by XRD, FE-SEM, TEM, ICP and N2adsorption tests and their H2storage was also measured. The results show that the composites contain a large amount of Pd and have a regular mesoporous structure, and Pd particles with a diameter of 2-6 nm are evenly dispersed between graphene sheets and pillar the graphene sheets. The BET surface area of the composites is 230 m2/g and their H2storage reaches 3.4 wt.% at 77K and 0.11 MPa.

SiO2/PI composite films with different percentage of incorporated nanoSiO2 were synthesized. With the increase of the adding SiO2 content, the surface roughness and the fractal dimension increased by SEM characterization for the fracture surface, and the thermal property of SiO2/PI composite films improved. The results indicate that the degree of imidization of the polyimide was full, and the polymer structure transformed from disorder into order after SiO2 was added to the PI matrix.